The metal layer(s) in a semiconductor device are usually damaged from exposure of the metal layer to oxygen during the dielectric etching process. Even though the metal oxide created from the oxygen exposure is removed, for example, with an acidic solution, the exposure results in substantial diffusion and penetration of oxygen into the metal layer. Moreover, extensive metal oxide formation and subsequent removal can easily result in retrograde profiles in a structure, which will reduce the amount of metal available for assembly plating and wire bonding.
Thus there remains a need to develop methods for limiting oxidation to the surface of the metal layer to not only minimize the diffusion and penetration of oxygen in the metal layer, but also to avoid substantial reduction in the amount of metal available for assembly plating and wire bonding.